In recent years there has been considerable emphasis on wireless transfer of data in packet form. Such data might typically be transferred between items of data processing equipment such as computers in a local area network or in connection with telephonic transmission of voice data. Systems embodying such communications are normally operated in a limited geographical area such as the confines of a building or among several buildings in close proximity. The problem which commonly arises in such systems is that one cannot preclude interference from other sources of electromagnetic radiation.
In some regions, a frequency band may not be dedicated to such communications. The band may be shared with other sources, both communication devices and sources of electromagnetic noise whose interference is sometimes unpredictable. One approach to reducing interference is to employ spread spectrum encoding and decoding of signals. This enhances noise rejection, but does not render a communication system immune to all other transmission sources. One particular problem relates to use of microwave appliances which may be operating in a nominal frequency band proximate to the frequency band of a communication system. The frequency of signals emanating from such an appliance can vary radically during operation, and such devices consequently tend to jam transmissions in a very aggressive manner.